U.S. patent application number 12/794998 was filed with the patent office on 2010-09-23 for lighting or signaling device comprising a curved light guiding plate.
This patent application is currently assigned to VALEO VISION. Invention is credited to Antoine De Lamberterie, Christophe Dubosc.
Application Number | 20100238675 12/794998 |
Document ID | / |
Family ID | 37734300 |
Filed Date | 2010-09-23 |
United States Patent
Application |
20100238675 |
Kind Code |
A1 |
Dubosc; Christophe ; et
al. |
September 23, 2010 |
LIGHTING OR SIGNALING DEVICE COMPRISING A CURVED LIGHT GUIDING
PLATE
Abstract
A lighting or signaling device for a motor vehicle which is
capable of emitting a linear beam in the direction of an optical
axis and which comprises a point light source that emits light rays
radially around a source; a light ray guiding plate; wherein the
light guiding plate is shaped so that the light rays generally
propagate in incident propagation planes normal to the plate
between the light source and the reflection edge and in reflected
propagation planes normal to the plate between the reflection edge
and the output edge.
Inventors: |
Dubosc; Christophe;
(Villemomble, FR) ; De Lamberterie; Antoine;
(Paris, FR) |
Correspondence
Address: |
MATTHEW R. JENKINS, ESQ.
2310 FAR HILLS BUILDING
DAYTON
OH
45419
US
|
Assignee: |
VALEO VISION
Bobigny Cedex
FR
|
Family ID: |
37734300 |
Appl. No.: |
12/794998 |
Filed: |
June 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11780672 |
Jul 20, 2007 |
7731400 |
|
|
12794998 |
|
|
|
|
Current U.S.
Class: |
362/518 ;
362/509; 362/516 |
Current CPC
Class: |
F21S 43/243 20180101;
F21S 43/239 20180101; F21S 43/14 20180101; F21Y 2115/10 20160801;
F21S 43/249 20180101 |
Class at
Publication: |
362/518 ;
362/509; 362/516 |
International
Class: |
F21V 7/00 20060101
F21V007/00; F21V 1/00 20060101 F21V001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 21, 2006 |
FR |
06 06 718 |
Claims
1. A lighting or signaling device for a motor vehicle which is
capable of emitting a linear beam essentially in a direction of an
optical axis, and which comprises: a light source; a light ray
guiding plate that comprises an edge for inputting light rays, a
front edge for outputting said light rays tangentially to said
light ray guiding plate, and a rear edge for reflecting said light
rays coming from said light source in a direction of an output
edge; wherein said light ray guiding plate comprises an area for
coupling with said light source shaped so that said light rays
emitted by said light source are propagated radially at said area
for coupling around a source axis, wherein said light ray guiding
plate is shaped so that said light rays propagate in meridian
incident propagation planes normal to said light ray guiding plate
between said light source and said rear edge for reflecting, in
reflected propagation planes normal to said light ray guiding plate
between said rear edge for reflecting and said output edge, and
wherein said rear edge for reflecting is shaped so that said
reflected propagation planes have an orientation with respect to
the optical axis such that said lighting or signaling device is
capable of emitting a linear light beam along an essentially
longitudinal optical axis.
2. The lighting or signaling device according to claim 1, wherein
said reflected propagation planes are parallel to said optical axis
of said lighting or signaling device.
3. The lighting or signaling device according to claim 1, wherein
said reflected propagation planes are orthogonal to said output
edge.
4. The lighting or signaling device according to claim 1, wherein
said light ray guiding plate has a curved shape.
5. The lighting or signaling device according to claim 4, wherein
at least a first rear portion of said light ray guiding plate which
is delimited by an angular sector extending from a source axis and
which surrounds a reflection, has a shape of a portion of base
sphere.
6. The lighting or signaling device according to claim 5, wherein
said source axis passes through a center of said base sphere.
7. The lighting or signaling device according to claim 6, wherein a
second front portion of said light ray guiding plate forms a solid
of revolution around said optical axis that passes through said
center of said base sphere.
8. The lighting or signaling device according to claim 6, wherein
said reflected propagation planes are secants along said optical
axis.
9. The lighting or signaling device according to claim 1, wherein
at least two light ray guiding plates are arranged in a first
stratum, at least a third light ray guiding plate being arranged in
a second stratum, each light ray guiding plate being a portion of a
base sphere.
10. The lighting or signaling device according to claim 9, wherein
said light ray guiding plates of said first stratum are portions of
a first common base sphere, and in that said light ray guiding
plates of said second stratum are portions of a second common base
sphere, all said light ray guiding plates being centered on a
common center.
11. The lighting or signaling device according to claim 9, wherein
said light ray guiding plates have different axes and different
radii of curvature.
12. The lighting or signaling device according to claim 1, wherein
said output edge comprises means for defining a spread of a light
beam around a direction of said optical axis in said reflected
propagation plane.
13. The lighting or signaling device according to claim 1, wherein
said light ray guiding plate is flat.
14. The lighting or signaling device according to claim 13, wherein
said output edge is essentially flat, said rear edge for reflecting
having at least one parabolic shape whereof a directrix forms an
angle with the normal to the output edge such that the light rays
are parallel or essentially parallel to the optical axis once
refracted by said output edge.
15. The lighting or signaling device according to claim 13, wherein
said output edge is curved, said rear edge for reflecting having a
complex shape such that, for any point on said output edge, any ray
reflected by said rear edge for reflecting arriving at this point
on said output edge is refracted parallel to said optical axis.
16. The lighting or signaling device according to claim 1, wherein
said output edge comprises means for defining a spread of a light
beam in a plane tangential to said light ray guiding plate.
17. The lighting or signaling device according to claim 16, wherein
said output edge comprises flutes that are capable of deviating
outgoing light rays by refraction in a plane tangential to said
light ray guiding plate.
18. The lighting or signaling device according to claim 16, wherein
said light ray guiding plate comprises holes that are arranged in
proximity to said output edge, said light rays being deviated from
their path in a tangential plane by passing through a wall of a
hole before entering said light ray guiding plate again in
direction of said output edge.
19. The lighting or signaling device according to claim 1, wherein
said edge for inputting light rays comprises a front portion that
is shaped so as to disperse said light rays coming from said light
source heading directly towards said output edge.
20. A lighting or signaling device for a motor vehicle, said
lighting or signaling device capable of emitting a light beam in a
general direction of an optical axis, and which comprises: a light
source; a light ray guiding plate comprising a coupling area
adapted so that light rays emitted by said light source are
propagated generally radially at a coupling area in operative
relationship with a light source axis, wherein said light ray
guiding plate is adapted so that said light rays generally
propagate in reflected propagation planes comprising an orientation
with respect to said optical axis such that said lighting or
signaling device is capable of emitting a generally linear light
beam along a generally longitudinal optical axis.
21. The lighting and signaling device according to claim 20,
wherein said light ray guiding plate that comprises an edge for
inputting said light rays, a front edge for outputting said light
rays generally tangentially to said light ray guiding plate, and a
rear edge for reflecting said light rays coming from said light
source in a general direction of an output edge.
22. The lighting and signaling device according to claim 20,
wherein said light ray guiding plate has a curved shape.
23. The lighting and signaling device according to claim 22,
wherein said reflected propagation planes are generally parallel to
said optical axis of said lighting device.
24. The lighting and signaling device according to claim 22,
wherein said reflected propagation planes are generally orthogonal
to said output edge.
25. The lighting and signaling device according to claim 20,
wherein at least two light ray guiding plates are arranged in a
first stratum, at least a third light ray guiding plate being
arranged in a second stratum, each light ray guiding plate being a
portion of a base sphere.
26. The lighting and signaling device according to claim 21,
wherein said edge for outputting said light rays comprises means
for defining a spread of said light beam around a direction of said
optical axis in said reflected propagation plane.
27. The lighting or signaling device according to claim 21, wherein
said output edge is essentially flat, said rear edge for reflecting
having at least one parabolic shape whereof a directrix forms an
angle with a normal to said output edge such that said light rays
are parallel or essentially parallel to said optical axis once
refracted by said output edge.
28. The lighting or signaling device according to claim 21, wherein
said output edge is curved, said rear edge for reflecting having a
complex shape such that, for any point on said output edge, any ray
reflected by said rear edge for reflecting arriving at this point
on said output edge is refracted parallel to said optical axis.
29. The lighting or signaling device according to claim 21, wherein
said output edge comprises means for defining a spread of said
light beam in a plane tangential to said light ray guiding
plate.
30. The lighting or signaling device according to claim 21, wherein
said edge for inputting said light rays comprises a front portion
that is shaped so as to disperse said light rays coming from said
light source heading directly towards said output edge.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
11/780,672 filed Jul. 20, 2007, which is incorporated herein by
reference and made a part hereof. This application also claims
priority to French Application No. 0606718 filed Jul. 21, 2006,
which application is incorporated herein by reference and made a
part hereof.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention concerns a lighting or signaling device for a
motor vehicle which comprises a plate for guiding the light.
[0004] The invention more particularly concerns a lighting or
signaling device for a motor vehicle which is capable of emitting a
linear beam essentially in the direction of an optical axis, and
which comprises:
[0005] a point light source that emits light rays radially around a
source axis; and
[0006] a light ray guiding plate that comprises an edge for
inputting the light rays, a front edge for outputting the light
rays tangentially to the light guiding plate, and a rear edge for
reflecting the light rays coming from the light source in the
direction of the output edge.
[0007] 2. Description of the Related Art
[0008] It is common practice to group several lighting and/or
signaling functions together in a single enclosure, so as to
simplify the electrical wiring for these different functions in a
motor vehicle.
[0009] Moreover, the shape of the lighting and/or signaling lights
plays a leading role in the search for a style and original
aesthetics which will enable the motor vehicle to be recognized
from a distance.
[0010] To solve these problems, equipping the vehicle with light
guides is known. A light guide is a cylinder of transparent
material which forms a kind of "pipe" into which the light rays
enter via a first input end. The light rays are then guided along
the light guide by successive total reflections on its cylindrical
outer face.
[0011] A rear portion of the cylindrical face of the light guide
comprises irregularities, such as diffusion flutes, which make it
possible to diffuse some of the light rays towards the front so
that some of the diffused light rays exit the light guide by
passing through the opposite portion of the cylindrical face in
order to form a light beam.
[0012] The light guide can for example be shaped as a ring that
surrounds the front boundary of a low beam headlamp so as to emit
an annular light beam. The input end portion of the light guide is
then bent so that the light ray input end is arranged outside the
ring formed by the light guide.
[0013] However, such a solution does not make it possible to obtain
a high intensity light beam. This is because the light rays emitted
by the light source are guided in a random and unordered manner
inside the light guide. Moreover, only some of the light rays are
diffused to the outside by the irregularities. Consequently, the
light beam obtained by such a device is very weak even if the light
source arranged at the input end of the light guide is very
powerful.
[0014] However, certain lighting and signaling functions require a
very intense light beam in order to comply with current
regulations. The light guide is therefore not suitable for
implementing such functions.
[0015] Moreover, the appearance of the annular beam obtained is
highly non-uniform in particular for the following two reasons.
[0016] On the one hand the material constituting the lighting or
signaling device brings about some absorption of the light rays
that pass through it, which results in losses that become greater
with the distance away from the light source. As a result the
brightness in the vicinity of the light source is greater than at a
distance from this source, hence a uniformity fault.
[0017] On the other hand some of the light rays introduced into the
light guide via the bent input portion directly reach the opposite
face of the light guide thus causing the appearance of a spot that
is very bright compared with the rest of the annular beam.
[0018] There is, therefore, a need to provide an improved lighting
or signaling device.
SUMMARY OF THE INVENTION
[0019] To solve these problems, the invention proposes a lighting
or signaling device for a motor vehicle comprising a light source
and a light ray guiding plate which comprises an edge for inputting
the light rays, a front edge for outputting the light rays
tangentially to the light guiding plate, and a rear edge for
reflecting the light rays coming from the light source in the
direction of the output edge, in which:
[0020] the light guiding plate comprises an area for coupling with
the light source shaped so that the light rays emitted by the light
source are propagated radially at the coupling area around a source
axis;
[0021] the light guiding plate is shaped so that the light rays
propagate in meridian incident propagation planes normal to the
plate between the light source and the reflection edge, and in
reflected propagation planes normal to the plate between the
reflection edge and the output edge; and
[0022] the reflection edge is shaped so that the reflected
propagation planes have an orientation with respect to the optical
axis such that the lighting device is capable of emitting a linear
light beam along an essentially longitudinal optical axis.
[0023] According to other characteristics of the invention:
[0024] the reflected propagation planes are parallel to the optical
axis of the lighting device;
[0025] the reflected propagation planes are orthogonal to the
output edge;
[0026] the light guiding plate (12) has a curved shape;
[0027] at least a first rear portion of the light guiding plate
which is delimited by an angular sector extending from the source
axis and which surrounds the reflection edge, has the shape of a
portion of base sphere;
[0028] the source axis passes through the center of the base
sphere;
[0029] a second front portion of the light guiding plate forms a
solid of revolution around the optical axis that passes through the
center of the base sphere;
[0030] the reflected propagation planes are secants along the
optical axis;
[0031] at least two light guiding plates are arranged in a first
stratum, at least a third light guiding plate being arranged in a
second stratum, each light guiding plate being a portion of a base
sphere;
[0032] the light guiding plates of the first stratum are portions
of a first common base sphere, and in that the light guiding plates
of the second stratum are portions of a second common base sphere,
all the light guiding plates being centered on a common center;
[0033] the light guiding plates have different axes and different
radii of curvature;
[0034] the light ray output edge comprises means for defining the
spread of the light beam around the direction of the optical axis
in the reflected propagation plane;
[0035] the output edge is shaped like a lens in order to deviate
the light rays by refraction;
[0036] the light guiding plate is flat;
[0037] the output edge forms an angle with the normal to the
optical axis at several of its points and is capable of refracting
the outgoing light rays, the reflection edge being shaped so that
the reflected propagation planes have an orientation with respect
to the output edge such that the light rays are essentially
parallel or parallel to the optical axis once refracted by the
output edge; in the absence of flutes on the output edge, the light
rays refracted by the output edge will be parallel to the optical
axis; in the presence of flutes spreading the light horizontally,
the light rays refracted by the output edge will be essentially
parallel to the optical axis, and the beam exiting each flute will
be centered on an axis parallel to the optical axis;
[0038] the output edge is essentially flat, the reflection edge
having at least one parabolic shape whereof the directrix forms an
angle with the normal to the output edge such that the light rays
are essentially parallel or parallel to the optical axis once
refracted by the output edge; in the absence of flutes on the
output edge, the light rays refracted by the output edge will be
parallel to the optical axis; in the presence of flutes spreading
the light horizontally, the light rays refracted by the output edge
will be essentially parallel to the optical axis, and the beam
exiting each flute will be centered on an axis parallel to the
optical axis;
[0039] the output edge is curved, the reflection edge having a
complex shape such that, for any point on the output edge, any ray
reflected by the reflection edge arriving at this point on the
output edge is refracted parallel to the optical axis;
[0040] the output edge comprises means for defining the spread of
the light beam in a plane tangential to the light guiding
plate;
[0041] the output edge comprises flutes that are capable of
deviating the outgoing light rays by refraction in a plane
tangential to the light guiding plate;
[0042] the light guiding plate comprises holes that are arranged in
proximity to the output edge, the light rays being deviated from
their path in a tangential plane by passing through the wall of the
hole before entering the light guiding plate again in the direction
of the output edge;
[0043] the holes are aligned in staggered rows parallel to the
output edge;
[0044] the light ray input edge comprises a front portion that is
shaped so as to disperse the light rays coming from the light
source heading directly towards the output edge;
[0045] the light source is a radially emitting LED and the light
guiding plate comprises an aperture having a peripheral edge that
corresponds to the input edge, the radially emitting LED being
placed inside the aperture;
[0046] the light source is an axially emitting LED and the light
guiding plate comprises a reflection surface corresponding to a
shape complementary to a cone whereof the axis of symmetry
corresponds to the source axis of the light source, this reflection
surface being arranged opposite the input edge in order to direct
the light rays radially in the light guiding plate;
[0047] preferentially the complementary shape comprises a part with
a conical profile and a flat part, the part with the conical
profile being surrounded by the reflection edge and the flat part
being oriented facing the output edge so that the rays emitted at
the flat part are reflected parallel to a preferred direction, for
example the optical axis; thus, all the rays arriving on the shape
with the conical profile are reflected towards the reflection edge,
whereas those which would not be able to reach this reflection edge
if the complementary shape had a completely conical profile, reach
the flat surface and are therefore reflected parallel; the optical
efficiency of the device is thus increased;
[0048] the light source is arranged at a distance from the input
edge, the emitted light rays being guided as far as the reflection
face in the shape of an angular sector of a cone with source axis
in order to direct the light rays radially solely towards the
reflection edge of the light guiding plate.
[0049] Other characteristics and advantages will emerge from a
reading of the following detailed description, for the
understanding of which reference should be made to the accompanying
drawings, amongst which:
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0050] FIG. 1 is a front view depicting a lighting device according
to the invention comprising a light guiding plate;
[0051] FIG. 2 is a detail view on a larger scale of the arrangement
of a light source in the light guiding plate of FIG. 1;
[0052] FIG. 3 is a bottom view of the light guiding plate of FIG.
1;
[0053] FIG. 4 is a side view depicting a variant of the light
source of FIG. 2;
[0054] FIG. 5 is a sectional view along the section plane 5-5 of
FIG. 3;
[0055] FIG. 6 is a view similar to that of FIG. 5 depicting a
variant embodiment of the invention;
[0056] FIG. 7 is a perspective view depicting a lighting device
that comprises a plurality of light guiding plates that are
arranged on a base sphere and in which the output edges of the
light guiding plates comprise flutes;
[0057] FIG. 8 is a detail perspective view depicting a variant
embodiment of the light guiding plates of FIG. 7;
[0058] FIG. 9 is a front view depicting an arrangement of several
light guiding plates in strata;
[0059] FIG. 10 is a top view of a lighting device according to the
invention comprising a flat light guiding plate;
[0060] FIG. 11 is a detail sectional view on a larger scale of the
arrangement of a light source in the light guiding plate of FIG.
1;
[0061] FIG. 12 is a detail sectional view of the arrangement of a
light source with the light guiding plate according to a variant
embodiment;
[0062] FIG. 13 is a detail sectional view of the arrangement of a
light source with the light guiding plate according to another
variant embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0063] Subsequently, identical, analogous or similar elements will
be designated by the same reference numbers.
[0064] For the remainder of the description, there will be adopted
on a non-limiting basis a longitudinal orientation fixed with
respect to the motor vehicle and directed from the rear to the
front which is indicated by the arrow "L" in FIGS. 1 and 2.
[0065] FIG. 1 depicts a lighting or signaling device 10 for a motor
vehicle. The lighting device 10 is capable of emitting a linear
light beam "F" along an essentially longitudinal optical axis A
(FIG. 1).
[0066] The lighting device 10 comprises in particular at least one
light guiding plate 12 which appears in the form of a portion of a
segment of a sphere. The lighting device 10 depicted in FIG. 1
comprises a single light guiding plate 12 forming a portion of an
imaginary base sphere 13.
[0067] For the remainder of the description, there will be adopted
locally at any point of the light guiding plate 12, and on a
non-limiting basis, a normal orientation N orthogonal to the light
guiding plate.
[0068] The light guiding plate 12 is thus delimited in the
thickness direction by a front face 14 and a rear face 16 for
guiding the light. The two faces, front 14 and rear 16, are
parallel to each other over at least part of the plate.
[0069] The light guiding plate 12 is in particular delimited
laterally by a front edge 18 for outputting the light rays and by a
rear edge 20 for reflecting the light. In the example depicted in
FIG. 1, the ends of the reflection edge 20 are connected directly
to the ends of the output edge 18 so as to form the external
boundary of the light guiding plate 12.
[0070] The reflection edge 20 can consist of a reflective plate,
such as an aluminized coating on the outer face of the reflection
edge 20. It can also be provided that, between the two junctions
between the reflection edge 20 and each of the faces 14 and 16 of
the light guiding plate 12, the output edge 18 has a ridge
extending along this edge and dividing it into two faces forming an
angle between them. Thus an incident ray RI (FIG. 3) will undergo a
double reflection, a first on one of the faces and a second on the
other face, in order to be emitted in the reflected propagation
plane "Mr". For ease of understanding, in FIG. 10, the plane "Mr"
in which the represented ray "RR" propagates is normal to the page
(of drawing) and is along the represented ray "RR". For example,
the plane "Mr" of FIG. 5 corresponds to plane 5-5 in FIG. 3.
[0071] The boundary of the light output edge 18 here forms a flat
arc of a circle, that is to say the boundary of the output edge is
defined by the intersection between the base sphere 13 and a
plane.
[0072] According to a variant of the invention depicted in FIG. 7,
the external boundary of the light guiding plate 12 also comprises
inactive transition areas 22 that are interposed between the
reflection edge 20 and the output edge 18.
[0073] As depicted in FIG. 2, the light guiding plate 12 also
comprises an aperture 24 that is delimited by a peripheral light
input edge 26. The aperture 24 is here a through aperture. A light
source 28 is arranged in the aperture 24 close to or in contact
with the light ray input edge 26.
[0074] The light source 28 is capable of emitting light rays in an
essentially radial direction around a source axis "S" that is
normal to the light guiding plate 12. More precisely, the light
source 28 is capable of emitting a fan of light rays radially at
least towards the rear in the direction of the reflection edge
20.
[0075] The light source 28 is here a so-called "Side Emitter" light
emitting diode or "LED" which emits light rays in a fan for example
of approximately 30.degree. either side of the radial direction in
a plane meridian to the source axis "S" and which is capable of
extending around the source axis "S", for example over 360.degree.
in a plane normal to the source axis "S".
[0076] As depicted in FIG. 11, the "side emitter" type LED is
disposed so that its emitting surface is in a through opening made
in an area "ZC" for coupling with the light source 28. Rays r
emitted radially by the LED are depicted and all start off in the
thickness of the coupling area "ZC". The emission cone C of the LED
is also depicted schematically, and approximately corresponds at
the input edge to the thickness of the light guiding plate. Thus
the coupling area "ZC" allows coupling between the light guiding
plate 12 and the light source 28, so that the light rays emitted by
the light source are propagated radially at the coupling area
around a source axis "S".
[0077] According to variants depicted in FIGS. 12 and 13, the
aperture opens out solely in one of the guidance faces of the light
guiding plate 12 but not in the other face. Thus in FIG. 12, the
source 28 is here a Lambertian type LED, or axially emitting LED.
Here, it is a LED lacking a dome, for example a LED available under
the trade name "Golden Dragon". It emits in a half-space. It is
disposed so that its emitting surface is flush with the surface of
the coupling area "ZC" which has been arranged so that the light
rays emitted by the light source are then redirected radially at
the coupling area around a source axis "S". The coupling area "ZC"
locally has an input area in the form of a convex rounded surface
"B" (FIG. 12) on the face on the side of which the LED 28 is
situated, and, on the opposite face and facing this convex face
"B", an area approximating the shape of a shape complementary to a
cone "CO". Two types of light ray emitted by this LED can be
distinguished: r1 type rays that directly enter the thickness of
the coupling area, and r2 type rays that are first refracted by the
surface B and then totally reflected by the walls of the cone "CO."
The emission cone "C" of the LED is also depicted.
[0078] According to the variant depicted in FIG. 13, a Lambertian
type LED with a protective dome is used this time. Such a LED is
for example known by the trade name "Led Rebel". The LED 28 is
disposed in the coupling area "ZC" so that the dome is inserted in
a non-through opening made in the coupling area. There is in this
opening a convex rounded surface "B'" and on the opposite face of
the coupling area a prepared surface of an area approximating the
shape of a shape complementary to a cone "CO" so that, as in FIG.
12, the rays that reach it set off again in the coupling area "ZC"
by total reflection. There are therefore found, as in FIG. 12, two
types of ray emitted by the LED: those of r1 type emitted towards
the sides that directly enter the coupling area, and those of r2
type that are first refracted on the surface B and then totally
reflected on the modified surface situated facing the surface
B.
[0079] The cone "CO" can also have a deformed area making it
possible to send back the rays that, without this area, would
directly reach the output edge. This concerns for example a kind of
"truncation" so that the reflection area "CO" has a flat face.
Thus, according to a section along a plane perpendicular to the
source axis "S" and approximately at the face of the light guiding
plate which is opposite the LED 28, the perimeter of the cone
corresponds to a circle. With the truncation, a section is obtained
in the form of a circle in which an arc of a circle has been
removed, a straight line connecting the two ends of the remaining
part of the circle. A flattened circle is therefore obtained. This
straight line constitutes the base of the triangle formed by the
truncation on the cone. The tip of this triangle opposite to this
base is situated on the cone between the two faces of the light
guiding plate, preferentially in proximity to the tip of the cone.
A cone with a flatted face is therefore obtained. This flattened
face is situated facing the output edge. All the rays emitted above
the part with the conical profile will therefore be distributed
around the source axis "S" inside an angular interval corresponding
to the circular part of the section of the cone on the face
opposite to the LED 28. Preferentially the tip of the flat face is
situated between the tip of the cone and the base thereof, on the
side of the output edge (for example on the left in FIGS. 12 and
13). Thus the angular interval is greater than 180.degree.. The
reflection edge surrounds this area with the conical profile and
therefore all the rays reflected around the source axis "S" are
reflected a second time by the reflection edge. On the other hand,
the rays emitted above the flat face will be reflected in the same
direction and directly towards the output edge, the base of the
triangle constituting the flat face perpendicular to the optical
axis.
[0080] In conclusion on the choice of LEDs, it can be seen that one
embodiment of the invention makes it possible to use LEDs with very
different characteristics, capable of emitting either radially, or
axially, or in a half-plane. It is then necessary to arrange the
coupling area accordingly, for example by making an opening that is
either through or not for inserting therein all or part of the LED,
and by providing optical means when necessary (in particular for
LEDs emitting in a half-plane) so that the maximum amount of the
light emitted by the LED propagates correctly in the thickness of
the coupling area without loss as far as the rear reflection area
20.
[0081] In the examples depicted, the light input edge 26 is thus
surrounded by the external boundary comprising the output edge 18
and by the reflection edge 20 of the light guiding plate 12. The
input edge 26 could however not be closed. This is because there is
a sector of this edge 26 that is not very effective, situated
opposite the reflection edge 20, and for which the rays reflected
by the edge 20 return towards the input edge 26. These light rays
are therefore not used in the lighting or signaling device, and
they are lost. Advantage can be taken of this observation to not
dispose any material in this region, in order to thus facilitate
the removal of the light guiding plate from the mould.
[0082] The light guiding plate 12 is made from a transparent
material whereof the refractive index is higher than the refractive
index of the medium in which the lighting device 10 is intended to
be immersed, air for example. Thus, a light ray introduced into the
thickness of the plate 12 via its input edge 26 with an incident
angle with respect to the normal "N" which is greater than a
critical angle of refraction is capable of being totally reflected
by the guidance faces 14, 16.
[0083] The light ray is therefore guided in the thickness of the
light guiding plate by successive reflections between the two
guidance faces 14, 16.
[0084] As depicted in FIG. 3, the incident light rays that start
off towards the rear are intended to be reflected by the reflection
edge 20, and then the light rays thus reflected are directed
towards the output edge 18. The reflected light rays thus exit via
the output edge 18 tangentially to the light guiding plate 12 in
order to form the linear light beam "F" in an arc of a circle.
[0085] For the remainder of the description, an incident light ray
will be defined as a light ray that is emitted by the light source
28 in the direction of the reflection edge 20. The light rays
emitted by the light source 28 directly in the direction of the
output edge 18 are therefore not included in this definition of
incident rays. The light rays that are emitted towards the front by
the light source 28 directly in the direction of the output edge 18
will be referred to as "direct".
[0086] The light source 28 can also consist of an incandescent
bulb, for example a halogen bulb, with axial filament, inserted
within the boundary delimited by the input edge 26. Provision can
then advantageously be made in this case that an area of the light
guiding plate, in the vicinity of the input edge 26, is made of
glass, while the remainder of the plate will be made of plastic
overmolded on this glass area. Such a design makes it possible to
avoid thermal problems that could be generated by the use of an
incandescent source.
[0087] To avoid the input edge 26 being visible by an observer
situated in the axis A, or more exactly to avoid this observer
seeing a light spot, corresponding to the light source, surrounded
by two black points, corresponding to the upper and lower faces of
the input edge 26, it is advantageous to see to it that each point
on the portion of the input edge 26 corresponding to the direct
rays re-emits light towards a given area of the output edge.
[0088] For example a complex shape 29 can be given to the input
edge 26, so that the light rays are collimated in the plane
tangential to the plate, in order that these light rays reach a
reduced area of the output edge 18. The addition of flutes on this
complex shape 29 then makes it possible to optimize the
concentration of the rays reaching the area of the output edge 18,
and consequently also the size of this area of the output edge 18,
in order that this area does not appear brighter than the rest of
the boundary for an observer situated in the axis.
[0089] The portion of input edge 26 which is oriented towards the
front is thus shaped so as to distribute the direct light rays
substantially uniformly along the output edge 18. As depicted in
FIG. 2, the front portion 29 of the input edge 26 is serrated so as
to disperse the light rays into a fan that covers at least the
whole of the output edge 18.
[0090] So that the direct light rays are collimated in the plane
tangential to the plate, it is also possible to place on the area
of the input edge corresponding to the direct rays, in front of the
LED with respect to the optical axis, an area with the shape of a
convex curved surface, facing the LED 28, the surface being curved
in the direction of the LED. For example, the curved area can be
put in place of the serrated area 29 depicted in FIG. 2. According
to a variant embodiment, depicted in FIG. 10, the aperture inside
which the LED 28 is placed has a shape such that it has on the one
hand a concave shape, behind the LED 28 with respect to the optical
axis "A" of the lighting device and whereof the cross-section is
preferentially a semi-circle, and on the other hand a convex curved
shape in front of the LED. The concave shape and the convex shape
are separated by a flat portion, making it possible to position the
light source closer to the concave shape behind than to the convex
shape in front. The convex shape is thus moved further away from
the source and the cross-section of the cone of direct rays
reaching the convex shape is thus reduced. Some of the rays will
thus reach the flat part and will be refracted in the direction of
the reflection face. The amount of reflected rays is thus
increased. It should be noted that, for the sake of clarity, only
the aperture is depicted in FIG. 10; the LED 28 is not depicted but
its reference indicates its position within the aperture.
[0091] Similarly, provision can be made that the input edge 26 is
in the shape of a slightly truncated cone, so as to optimize the
mean direction of the rays in the plate in the meridian plane with
respect to the tangent to the plate.
[0092] According to a variant depicted in FIG. 4, the light source
28 is arranged in proximity to the input edge 26. The light source
28 is associated with a reflection face 30 which is arranged
opposite the light ray input edge. The reflection face 30 is shaped
so as to reflect the light rays essentially radially towards the
input edge 26 of the light guiding plate 12. The light rays coming
from the light source 28 are for example conducted to the
reflection face 30 by a light guide 32, an optical fiber (not
depicted), or a reflector (not depicted) which focuses the light
rays towards the reflection face 30.
[0093] The light source 28 is for example a halogen bulb or a light
emitting diode.
[0094] In the example depicted in FIG. 4, the light rays are guided
so as to reach the reflection face 30 essentially along the source
axis "S". The reflection face 30 is shaped as a cone of revolution
or a portion of cone of revolution with source axis "S" so as to
reflect the rays radially in a ring around the source axis "S".
[0095] Advantageously, the reflection face 30 is shaped as a rear
portion of cone so as to produce no "direct" light rays but only
"incident" light rays.
[0096] Advantageously, the reflection face 30 forms an upper end
face of the light guide 32 and the light guide 32 is made in one
piece of material with the light guiding plate 12.
[0097] According to the teachings of the invention, the light
guiding plate 12 is designed so that the incident light rays
emitted towards the rear by the light source 28 propagate in the
light guiding plate 12 along so-called "incident" meridian
propagation planes "Mi" that radiate radially from the source axis
"S". Thus, each light ray is guided so as to follow a radial
direction inside the light guiding plate 12 as far as the
reflection edge 20. In FIG. 10, the plane "Mi" in which the
represented ray "RI" propagates is normal to the page (of drawing)
and is along the represented ray "RI".
[0098] Moreover, the light guiding plate 12 is also designed so
that the rays reflected by the reflection edge 20 propagate towards
the front along so-called "reflected" flat propagation planes that
are normal to the light guiding plate 12 between the reflection
edge 20 and the output edge 18. The reflection edge 20 is more
particularly shaped so that the reflected propagation planes "Mr"
are oriented parallel to the optical axis "A".
[0099] Thus, the reflected light rays are distributed parallel all
along the output edge 18 so that each point of the output edge
emits a substantially equal amount of light in the direction of the
optical axis A. In this way, the output edge is seen uniformly by
an observer looking at the output boundary in the axis A.
[0100] Advantageously, but non-limitatively, the reflected
propagation planes "Mr" are orthogonal to the output edge 18 so
that all the reflected light rays that reach the output edge 18
exit without loss of light intensity.
[0101] The reflection edge 20 is here perpendicular to the guidance
faces 14, 16 of the light guiding plate 12.
[0102] This design is made possible on the one hand by the base
sphere portion shape 13 of at least one rear portion 12R of the
light guiding plate which is passed through by the incident light
rays between the light source 28 and the reflection edge 20, and on
the other hand by the particular shape given to the boundary of the
reflection edge 20.
[0103] The rear portion 12R forms at least one angular sector
extending from the source axis "S" and which surrounds the
reflection edge 20.
[0104] On account of the rounded shape as a portion of base sphere
13 of the rear portion 12R of the light guiding plate 12, the
reflected propagation planes "Mr" are secants along the same axis
which passes through the center "O" of the base sphere and which is
coincident with the optical axis "A". Moreover, the source axis "S"
is a secant with the optical axis "A" at the center "O" of the base
sphere.
[0105] Furthermore, the boundary of the reflection edge 20 is
defined mathematically by the following equation:
{right arrow over (dOM)} ({right arrow over (u.sub.i)}-{right arrow
over (u.sub.r)})={right arrow over (0)}
[0106] "O" being the center of the base sphere of the rear portion
of the light guiding plate 12;
[0107] "M" being any point on the reflection edge 20;
[0108] {right arrow over (dOM)} being the differential of the
vector OM, that is to say the tangent at M to the boundary of the
reflection edge 20;
[0109] {right arrow over (u.sub.i)} being a unit vector orthogonal
to the incident meridian plane "Mi" passing through the point
"M";
[0110] {right arrow over (u.sub.r)} being a unit vector orthogonal
to the reflected propagation plane "Mr" passing through the point
"M".
[0111] This equation expresses the fact that the image of an
incident propagation plane "Mi" by the reflection edge 20 is a
propagation plane "Mr".
[0112] This differential equation is capable of being solved either
by analytical means or numerically using a computer.
[0113] When the radius of the base sphere 13 tends to infinity, the
light guiding plate 12 can be considered as flat. The reflection
edge 20 then has the shape of a parabola and the reflected
propagation planes "Mr" are parallel to one another.
[0114] However, when the radius of the base sphere 13 is finite,
the shape of the reflection edge cannot be likened to a
parabola.
[0115] The light guiding plates 12 depicted in the figures are here
portions of segments of a sphere.
[0116] According to a non-depicted variant of the invention, the
light guiding plate 12 has a more complex shape. To comply with the
conditions described previously, it is however essential that a
rear portion 12R of the light guiding plate 12 forms a portion of
the base sphere.
[0117] On the other hand, whilst complying with the condition
according to which the reflected propagation planes "Mr" are
secants along the optical axis "A" and orthogonal to the light
guiding plate 12, the other front portion 12F of the light guiding
plate 12 which is passed through solely by the reflected rays can
have various shapes. To do this, the guidance faces 14, 16 form
surfaces of revolution around the optical axis "A" passing through
the center "O" of the base sphere 13.
[0118] The radii of curvature of the cross-section of the light
guiding plate 12 along the reflected propagation plane "Mr" are
advantageously sufficiently large to avoid the incident light rays
reaching one of the guidance faces 14, 16 with an angle greater
than the critical angle of refraction and exiting the light guiding
plate 12 before reaching the output edge 18.
[0119] For example, the light guiding plate 12 can have a front
portion of flared shape.
[0120] According to another aspect of the invention, depending on
the characteristics of the light beam "F" it is sought to obtain,
the light guiding plate 12 is supplemented by known optical systems
for focusing or on the contrary spreading the light rays forming
the light beam "F" in a meridian plane and/or in a plane tangential
to the light guiding plate 12.
[0121] To that end, the output edge 18 of the light guiding plate
is here shaped as a linear lens.
[0122] The output edge 18 is for example inclined with respect to a
direction normal to the plate 12 as depicted in FIG. 5. Thus, the
outgoing light rays are deviated by refraction so as to diverge or
on the contrary be focused parallel to the optical axis "A".
[0123] According to a variant depicted in FIG. 6, the plate 12
widens out in proximity to the output edge 18, which is itself
rounded here, so as to focus the light rays in the reflected
propagation plane "Mr".
[0124] As depicted in FIG. 7, the output edge 18 can also be
provided with radial flutes 34 so as to spread the light in a plane
tangential to the light guiding plate 12 in order that the light
beam "F" is visible by an observer who is situated at an angle with
respect to the optical axis "A".
[0125] According to a variant of the invention which is depicted in
FIG. 8, the flutes 34 are replaced by holes 36 which are made in
the light guiding plate 12 in proximity to the output edge 18. The
holes 36 are here aligned in staggered rows parallel to the output
edge 18. The boundary of the holes is produced so that the
reflected rays are deviated by refraction in a divergent manner on
arriving at the hole 36 before again entering the light guiding
plate 12 in the direction of the output edge 18. The arrangement of
the holes 36 in staggered rows makes it possible to not allow any
way out via which reflected rays would reach the output edge 18
without passing through a hole 36.
[0126] According to another aspect of the invention, as depicted in
FIG. 7, a plurality of light guiding plates 12 forming portions of
a common base sphere 13 can be arranged so as to obtain a set of
light beams forming a single beam, either a closed annular one or
in an open arc of a circle.
[0127] The boundary of the output edge 18 is then defined as the
intersection between the base sphere and a plane perpendicular to
the optical axis "A".
[0128] According to a variant of the invention depicted in FIG. 9,
the light guiding plates are arranged in a first spherical inner
stratum of four light guiding plates 12 which are portions of a
first common base sphere and in a second spherical outer stratum of
three light guiding plates 12 which are portions of a second common
base sphere. All the light guiding plates 12 are centered on a
common center "0". Thus, two concentric annular beams can be
obtained with a lighting or signaling device 10 of reduced size.
The light guiding plates 12 of the two strata are arranged in
staggered rows so that the light sources 28 are offset annularly
with respect to one another around the optical axis "A".
[0129] According to a non-depicted variant of the invention, it is
also possible to obtain a light beam "F" of non-circular shape by
means of light guiding plates whereof the output edge 18 is not in
the shape of a flat arc of a circle. Thus, the boundary of the
output edges 18 is obtained by the intersection between a base
sphere and any surface whatsoever.
[0130] It is for example possible to arrange several light guiding
plates which have different axes and different radii or curvature,
for example for producing any boundary whatsoever consisting of
several arcs of circles.
[0131] For example, in order to obtain a light beam "F" forming an
elliptical ring, the boundary of the output edges 18 is obtained by
the intersection between the base sphere 13 and a cylindrical
surface of revolution. The output edges 18 then have a skewed
boundary, that is to say one that is not flat. The light rays must
therefore be redirected, for example by flutes 34, at their exit
from the light guiding plate 12 in order to be directed in the
essential direction of the optical axis "A".
[0132] By virtue of the lighting or signaling device 10 according
to the invention, the light rays coming from the light source 28
reach the output edge 18 without losing their intensity. This
design therefore makes it possible to obtain a light beam "F" of
linear shape, here in the shape of an arc of a circle.
[0133] Such a lighting or signaling device 10 has good efficiency,
that is to say the intensity of the emitted light beam "F" is
scarcely less strong than the intensity of the light source 28. For
example, the light beam "F" can have an intensity of 600 Cd for a
light source with a luminous flux of 25 Lm.
[0134] In general terms, it should be understood that the rear
portion 12R of the light guiding plate 12 is advantageously a
portion of base sphere in order to optimize the intensity of the
light beam as much as possible.
[0135] However, the invention is also applicable to light guiding
plates that have a shape of a portion of base ellipsoid that
differs little from a base sphere so that the light rays deviate
slightly from the propagation planes "Mr" and/or "Mi" without the
intensity of the light beam being substantially degraded. This is
the case in particular for ellipsoids whereof the diameters have
relatively close dimensions.
[0136] The invention also concerns flat plates, such as for example
that depicted in FIG. 10, where the shaping of the reflection edge
20 is determined according to the shape and/or orientation of the
output edge 18, so that any incident ray "RI" emitted by the light
source 28 is reflected by the reflection edge 20 as a reflected ray
"RR" contained in a reflected reflection plane normal to the light
guiding plate and making a given angle with the output face 18,
such that this ray is refracted by the output face 18 as a light
ray "RS" exiting the plate parallel to the optical axis "A".
[0137] According to FIG. 10, the output edge 18 is substantially
straight and non-perpendicular to the optical axis "A", therefore
forming a given angle with the normal to this optical axis. For
outgoing rays "RS" parallel to the optical axis, the angle between
these outgoing rays and the normal "N" to the output edge 18 is
equal to that between the optical axis "A" and that same normal
"N". The refractive index of the plate is known and also that of
the medium in which the outgoing ray "RS" is travelling. A direct
relationship, such as a Descartes equation, therefore makes it
possible to obtain the angle of the reflected rays "RR" with the
normal "N" to the output edge 18, hereinafter referred to as the
"angle of parallel refraction". The reflection edge 20 is formed
from three parabolas, with a light source 28 disposed at each of
their foci. The reflected rays "RR" are therefore contained in
reflected propagation planes parallel to the directrices "D" of the
parabolas. Thus, by choosing an orientation of the reflection edge
20 so that the directrices "D" of the parabolas make an angle with
the normal to the output edge 18 which corresponds to the angle of
parallel refraction, the incident rays "RI" will be reflected by
the reflection edge 20 as reflected rays "RR", which will
themselves be refracted by the output edge 18 as outgoing rays "RS"
parallel to the optical axis "A".
[0138] Three parabolas have been depicted but this is not limiting.
In fact fewer or more can be provided. By using more parabolas and
limiting them on the side, the distance from the focus of the
parabola to the output edge is reduced, thus allowing the use of
shallower light guiding plates.
[0139] According to a non-depicted variant embodiment, the output
edge can have a non-straight shape, for example rounded. Under
these conditions the shape of the reflection edge will have a
complex shape, that is to say a shape distinct from a parabola,
ellipse or other simple geometric shapes. For each portion of the
output edge, positioning and orientation of the reflection edge are
determined, such that the angle of the reflected ray "RR" is
refracted as an outgoing ray "RS" parallel to the optical axis
"A".
[0140] It is possible to place flutes on the output edge,
irrespective of the boundary of the output curve. These are flutes
or holes 36 as defined previously, in order to make the
distribution of the light intensity uniform over the output edge.
Moreover, the rays exiting each flute will be distributed laterally
but centered around the optical axis A.
[0141] According to another variant embodiment, the output edge is
perpendicular to the optical axis, the reflection edge forming at
least one parabola in the plane of the light guiding plate and
whereof the directrix is parallel to this optical axis. The
reflected rays are then contained in reflected propagation planes
parallel to the optical axis. The output edge is preferentially
provided with flutes or holes 36 as defined previously, in order to
make the distribution of the light intensity uniform over the
output edge. The rays exiting each flute will be distributed
laterally but centered around the optical axis A.
[0142] While the form of apparatus herein described constitutes a
preferred embodiment of this invention, it is to be understood that
the invention is not limited to this precise form of apparatus, and
that changes may be made therein without departing from the scope
of the invention which is defined in the appended claims.
* * * * *